Antarctica is the continent at the extreme southernlatitudes of the Earth, containing the South Pole. It is surrounded by the Southern Ocean and divided in two by the Transantarctic Mountains. On average, it is the coldest, driest, windiest, and highest of all the continents. With 98% of it covered in ice, Antarctica, at 14 million km², is the third-smallest continent (after Europe and Australia). Because there is little precipitation, the entire continent is technically a desert and is thus the largest in the world. There are no permanent human residents and only cold-adapted plants and animals survive there, including penguins, fur seals, mosses, lichens, and many types of algae. The name "Antarctica" comes from the Greekανταρκτικός (antarktikos), meaning "opposite the Arctic."<ref>{{cite web

Although myths and speculation about a Terra Australis ("Southern Land") go back to antiquity, the first sighting of the continent is commonly accepted to have occurred in 1821 by the Russian expedition of Mikhail Lazarev and Fabian Gottlieb von Bellingshausen. The continent was largely neglected in the 19th century because of its hostile environment, lack of resources, and isolated location.

Antarctica is not under the political sovereignty of any nation, although seven countries (Argentina, Australia, Chile, France, New Zealand, Norway and the United Kingdom) maintain territorial claims. Most other countries do not recognize these claims, and the claims of Argentina, Chile and the United Kingdom all overlap. Also, the United States and Russia reserve the right to territorial claims. Human activity on the continent is regulated by the Antarctic Treaty, which was signed in 1959 by 12 countries and prohibits any military activity, supports scientific research, and protects the continent's ecozone. Ongoing experiments are conducted by more than 4000 scientists of many different nationalities and with many different research interests.

Exploration

Belief in the existence of a Terra Australis—a vast continent located in the far south of the globe to "balance" the northern lands of Europe, Asia and north Africa—had existed since Ptolemy suggested the idea in order to preserve symmetry of landmass in the world. Depictions of a large southern landmass were common in maps such as the early 16th century Turkish Piri Reis map. Even in the late 17th century, after explorers had found that South America and Australia were not part of "Antarctica," geographers believed that the continent was much larger than its actual size. However, as Antarctica has no indigenous population, it was mostly unknown and unexplored until the 19th century.

About 98% of Antarctica is covered by the Antarctic ice sheet. The ice sheet is, on average, 2.5 kilometers (1.6 miles) thick. Despite its zero precipitation in some areas, the continent has approximately 90% of the world's fresh water, in the form of ice.<ref name="cia">Central Intelligence Agency Factbook Retrieved February 62006.</ref> Western Antarctica is covered by the West Antarctic Ice Sheet. The West Antarctic Ice Sheet has been of recent concern because of the possibility, real though small, of its collapse. If it does break down, ocean levels would rise by several meters in a relatively short period of time. Several Antarctic ice streams, which account to about 10% of the ice sheet, flows to one of the many Antarctic ice shelves.

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During the Cambrian period Gondwana had a mild climate. West Antarctica was partially in the northern hemisphere, and during this period large amounts of sandstones, limestones and shales were deposited. East Antarctica was at the equator, where sea-floor invertebrates and trilobites flourished in the tropical seas. By the start of the Devonian period (416 Mya) Gondwana was in more southern latitudes and the climate was cooler, though fossils of land plants are known from this time. Sand and silts were laid down in what is now the Ellsworth, Horlick and Pensacola Mountains. Glaciation began at the end of the Devonian period (360 Mya) as Gondwana became centered around the South Pole and the climate cooled, though flora remained. During the Permian period the plant life became dominated by fern-like plants such as Glossopteris, which grew in swamps. Over time these swamps became deposits of coal in the Transantarctic Mountains. Towards the end of the Permian period continued warming led to a dry, hot climate over much of Gondwana.<ref name="Stonehouse">{{cite book

Mesozoic era (250-65 Mya)

As a result of continued warming, the polar ice caps melted and much of Gondwana became a desert. In East Antarctica the seed fern became established, and large amounts of sandstones and shales were laid down at this time. The Antarctic Peninsula began to form during the Jurassic period (206-146 Mya), and islands gradually rose out of the ocean. Ginkgo trees and cycads were plentiful during this period, as were reptiles such as Lystrosaurus. In West Antarctica coniferforests dominated through the entire Cretaceous period (146-65 Mya), though Southern beech began to take over at the end of this period. Ammonites were common in the seas around Antarctica, and dinosaurs were also present, though only two Antarctic dinosaur species (Cryolophosaurus and Antarctopelta) have been described to date. It was during this period that Gondwana began to break up.

Gondwana breakup (160-23 Mya)

Africa separated from Antarctica around 160 Mya, followed by India in the early Cretaceous (about 125 Mya). About 65 Mya, Antarctica (then connected to Australia) still had a tropical to subtropical climate, complete with a marsupial fauna. About 40 Mya Australia-New Guinea separated from Antarctica and the first ice began to appear. Around 23 Mya, the Drake Passage between Antarctica and South America resulted in the Antarctic Circumpolar Current. The ice spread, replacing the forests that then covered the continent. Since about 15 Mya, the continent has been mostly covered with ice.<ref name="Trewby">{{cite book

Geology of present-day Antarctica

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The geological study of Antarctica has been greatly hindered by the fact that nearly all of the continent is permanently covered with a thick layer of ice. However, newer techniques such as remote sensing have begun to reveal the structures beneath the ice.

Climate

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Antarctica is the coldest place on Earth. It has little precipitation, with the South Pole getting almost none, making it a frozen desert. Temperatures reach a minimum of between −85 °C and −90 °C (−121 °F and −130 °F) in the winter and about 30 degrees higher in the summer months. Sunburn is often a health issue as the snow surface reflects over 90% of the sunlight falling on it.<ref name="weather">British Antarctic Survey. Weather in the Antarctic Retrieved February 92006.</ref> Eastern Antarctica is colder than its western counterpart because of its higher elevation. Weather fronts rarely penetrate far into the continent, leaving the center cold and dry. Despite the lack of precipitation over the central portion of the continent, ice there lasts for extended time periods. Heavy snowfalls are not uncommon on the coastal portion of the continent, where snowfalls of up to 1.22 meters (48 inches) in 48 hours have been recorded. Image:Friesland-St-Boris.jpg At the edge of the continent, strong katabatic winds off the polar plateau often blow at storm force. In the interior, however, wind speeds are often moderate. During summer more solar radiation reaches the surface at the South Pole than is received at the equator in an equivalent period.<ref name="cia" />

Antarctica is colder than the Arctic for two reasons. First, much of the continent is more than 3 km above sea level, and temperature decreases with elevation. Second, the Arctic Ocean covers the north polar zone. The ocean's relative warmth is transferred through the icepack and prevents temperatures in the Arctic regions from reaching the extremes typical of the land surface of Antarctica.

Depending on the latitude, long periods of constant darkness or constant sunlight mean that climates familiar to humans are not generally present on the continent. The aurora australis, commonly known as the southern lights, is a glow observed in the night sky near the South Pole. Another unique spectacle is diamond dust, a ground-level cloud composed of tiny ice crystals. It generally forms under otherwise clear or nearly clear skies, so people sometimes also refer to it as clear-sky precipitation. A sundog, a frequent atmospheric optical phenomenon, is a bright "spot" beside the true sun.<ref name="weather" />

Population

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Although Antarctica has no permanent residents, a number of governments maintain permanent research stations throughout the continent. The population of persons doing and supporting science on the continent and its nearby islands varies from approximately 4000 in summer to 1000 in winter. Many of the stations are staffed around the year.

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The first settlers of Antarctica (the world region situated south of the Antarctic Convergence) were English and American sealers who used to spend a year or more on South Georgia, from 1786 onward. During the whaling era, which lasted until 1966, the population of that island varied from over 1000 in the summer (over 2000 in some years) to some 200 in the winter. Most of the whalers were Norwegian, with an increasing proportion of Britons. The settlements included Grytviken, Leith Harbour, King Edward Point, Stromness, Husvik, Prince Olav Harbour, Ocean Harbour and Godthul. Managers and other senior officers of the whaling stations often lived together with their families. Among them was the founder of Grytviken, Captain Carl Anton Larsen, a prominent Norwegian whaler and explorer who adopted British citizenship in 1910. His family included his wife, three daughters and two sons.

Image:Fieldwork-Melnik.jpgThe first child born in the southern polar region was Norwegian girl Solveig Gunbjörg Jacobsen, born in Grytviken on 8 October1913, and her birth registered by the resident British Magistrate of South Georgia. She was a daughter of Fridthjof Jacobsen, the assistant manager of the whaling station, and of Klara Olette Jacobsen. Jacobsen arrived on the island in 1904 to become the manager of Grytviken, serving from 1914 to 1921; two of his children were born on the island<ref>R.K. Headland, The Island of South Georgia, Cambridge University Press, 1984.</ref>.

Emilio Marcos Palma was the first person born on the Antarctic mainland, at Base Esperanza in 1978, his parents being sent there along with seven other families by the Argentinean government to determine if family life was suitable in the continent. In 1986 Juan Pablo Camacho was born at the Presidente Eduardo Frei Montalva Base, becoming the first Chilean born in Antarctica. Several bases are now home to families with children attending schools at the station.<ref>The Antarctic SunQuestions and answers Retrieved February 92006.</ref>

Flora and fauna

Flora

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The climate of Antarctica does not allow much vegetation to exist. A combination of freezing temperatures, poor soil quality, lack of moisture and sunlight limit the chances for plants to exist. As a result, plant life is limited to mostly mosses and liverworts. The autotrophic community is made up of mostly protists. The flora of the continent largely consists of lichens, bryophytes, algae, and fungi. Growth generally occurs in the summer, and only for a few weeks at most.

The passing of the Antarctic Conservation Act brought several restrictions to the continent. The introduction of alien plants or animals can bring a criminal penalty, as can the extraction of any indigenous species. The overfishing of krill, which plays a large role in the Antarctic ecosystem, led officials to enact regulations on fishing. The Convention for the Conservation of Antarctic Marine Living Resources (CCAMLR), a treaty that came into force in 1980, requires that regulations managing all Southern Ocean fisheries consider potential effects on the entire Antarctic ecosystem.<ref name="cia" /> Despite these new acts, unregulated and illegal fishing, particularly of Patagonian toothfish, remains a serious problem. The illegal fishing of toothfish has been increasing, with estimates of 32,000 tonnes in 2000.<ref>BBC News. Toothfish at risk from illegal catches. Retrieved February 112006.</ref><ref>Australian Antarctic Division. Toothfish. Retrieved February 112006.</ref>

Politics

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As the only uninhabited continent, Antarctica has no government and belongs to no country. Various countries claim areas of it, but most other countries do not recognize those claims. The area between 90°W and 150°W is the only part of Antarctica not claimed by any country.<ref name="cia" />

Since 1959, claims on Antarctica have been suspended and the continent is considered politically neutral. Its status is regulated by the 1959 Antarctic Treaty and other related agreements, collectively called the Antarctic Treaty System. For the purposes of the Treaty System, Antarctica is defined as all land and ice shelves south of 60°S. The treaty was signed by 12 countries, including the Soviet Union and the United States. It set aside Antarctica as a scientific preserve, established freedom of scientific investigation, environmental protection, and banned military activity on that continent. This was the first arms control agreement established during the Cold War.

The Antarctic Treaty prohibits any military activity in Antarctica, such as the establishment of military bases and fortifications, the carrying out of military manoeuvres, or the testing of any type of weapon. Military personnel or equipment are only permitted for scientific research or for any other peaceful purposes.<ref>Scientific Committee on Antarctic Research. Antarctic Treaty Retrieved February 92006.</ref> The only documented large-scale land military maneuver was "Operación 90", undertaken ten years before the Antarctic Treaty by the Argentinian military.<ref>Antarctica Institute of Argentina. Argentina in Antarctica Retrieved February 92006.</ref>

Economy

Although coal, hydrocarbons, iron ore, platinum, copper, chromium, nickel, gold and other minerals have been found, they exist in quantities too small to exploit. The 1991 Protocol on Environmental Protection to the Antarctic Treaty prevents such struggle for resources. In 1998 a compromise agreement was reached to add a 50-year ban on mining until the year 2048, further limiting economic development and exploitation. The primary agricultural activity is the capture and offshore trading of fish. Antarctic fisheries in 2000-01 reported landing 112,934 tonnes.<ref name="cia"><ref>Santa Barbara City College Biological Sciences Importance of Antarctica Retrieved February 52006.</ref>

Research

Each year, scientists from 27 different nations conduct experiments not reproducible in any other place in the world but the Antarctic. In the summer more than 4000 scientists operate research stations; this number decreases to nearly 1000 in the winter.<ref name="cia" /> The McMurdo Station is capable of housing more than 1000 scientists, visitors, and tourists.

Researchers include biologists, geologists, oceanographers, physicists, astronomers, glaciologists, and meteorologists. Geologists tend to study plate tectonics in the Arctic region, meteorites from the outer space, and resources from the breakup of the supercontinent Gondwanaland. Glaciologists in Antarctica are concerned with the study of the history and dynamics of floating ice, seasonal snow, glaciers, and ice sheets. Biologists, in addition to examining the wildlife, are interested in how harsh temperatures and the presence of people affect adaptation and survival strategies in a wide variety of organisms. Medical physicians have made discoveries concerning the spreading of viruses and the body's response to extreme seasonal temperatures. Astrophysicists in Amundsen-Scott South Pole Station are able to study the celestial dome and cosmic microwave background radiation because of the ozone hole and the location's dry, cold environment. Antarctic ice serves as both the shield and the detection medium for the largest neutrino telescope in the world, built 2 km below Amundsen-Scott station. <ref>Antarctic Connection Science in Antarctica Retrieved February 42006.</ref>

Since the 1970s an important focus of study has been the ozone layer in the atmosphere above Antarctica. In 1985 3 British Scientests working on data they had gathered at Halley Station on the Brunt Ice Shelf discovered the exitence of a hole in this layer. In 1998 NASA satellite data showed that the Antarctic ozone hole was the largest on record, covering 27 million square kilometers. In 2002 significant areas of ice shelves disintegrated in response to regional warming.<ref name="cia" />

Meteorites from Antarctica are a relatively recent resource for study of the material formed early in the solar system; most are thought to come from asteroids, but some may have originated on larger planets. The first meteorites found in Antarctica were in 1912. In 1969 the Japanese discovered nine meteorites in Antarctica. Most of these meteorites have fallen onto the ice sheet in the last million years. Motion of the ice sheet tends to concentrate the meteorites at blocking locations such as mountain ranges, with wind erosion bringing them to the surface after centuries beneath accumulated snowfall. Compared with meteorites collected in more temperate regions on Earth, the Antarctic meteorites are relatively well preserved.<ref name="meteorite">NASA Meteorites from Antarctica Retrieved February 92006.</ref>

This large collection of meteorites allows a better understanding of the abundance of meteorite types in the solar system and how meteorites relate to asteroids and comets. New types of meteorites and rare meteorites have been found. Among these meteorites are pieces blasted off the moon, and probably Mars, by impacts. These specimens, particularly ALH84001 discovered by ANSMET, are at the center of the controversy about possible evidence of microbial life on Mars. Because meteorites in space absorb and record cosmic radiation, the time elapsed since the meteorite hit the Earth can be determined from laboratory studies. The elapsed time since fall, or terrestrial residence age, of a meteorite represents more information that might be useful in environmental studies of Antarctic ice sheets.<ref name="meteorite" />